Neural regeneration and plasticity will be studied in female rats (200-250g) during a six month period after either frontal (FC), lateral-frontal (LFC), complete (CC) or sham hypothalamic cuts produced by the stereotaxic placement of a small Halasz-type knife. Parameters selected for investigation are neuroendocrine function, hypothalamic neurotransmitter content, hypothalamic neural connections either interrupted or modified, sex and feeding behaviors. Postoperative intervals chosen for study (1, 7, 14, 21, 75, and 180 days) are similar for all parameters and in certain cases the same animal furnishes data for several parameters. Functional preoptico-tuberal-hypophyseal connections remaining postoperatively are evaluated using bilateral electrochemical stimulation (ECS) of the medial preoptic area rostral to all lesions. Pituitary release of luteinizing hormone (LH) after ECS is estimated by radioimmunoassay (RIA) of plasma LH during a 160min period. Catecholamine and acetylocholine content of hypothalamic nuclei is measured and correlated with function parameters. Sex and feeding behavior is evaluated before and after knife cuts and the role of estrogens in behavioral changes after cuts is also being studied. Modern antero-and retrograde tracing techniques are used to estimate hypothalamic and extrahypothalamic brain loci affected by knife cuts acutely and chronically.